Brassiere or “bra” wings are the portions of a bra that wrap around the sides and back of the wearer of the bra. Because the wing portions of a bra cooperate with the cups and shoulder straps to support the breasts, elastic material has generally been used in making the wing portions.
One known way to provide this elasticity is to construct the bra wings from a multi-layer material, for example one having two smooth outer facing layers, and an elastic layer sandwiched therebetween. This method of construction has the advantage of including smooth outer fabrics for contacting the skin of the wearer. However, as a practical matter, straps with sandwiched elastic layers generally need to use additional “facing” elastics, i.e., thin strips of elastic sewn or laminated along the edges of the wings, to provide a sufficient amount of elasticity to perform the required support functions. This is because the amount and thickness of Elastane, or other elastic fibers, that would be needed to perform the function by means of the sandwiched elastic layer alone would cause the overall wing be too heavy and bulky.
However, facing elastics have a significant disadvantage in that they can lead to “back roll,” the pinching of subcutaneous fat in the wearer's back between parallel strips of elastic. This can, in turn, lead to an unsightly result and embarrassment on the part of the wearer.
Another known way to provide the required elasticity in a bra wing is to make the bra wing from a foam material, such as the foam material used in bra cups. In this method, a foam layer is sandwiched, e.g., by lamination, between two layers of fabric. For example, known straps utilizing foam have been formed using a multi-layer structure having a first outer (top) facing layer of fabric material, a layer of glue, a sandwiched layer of foam, another layer of glue, and a second (bottom) outer facing layer of fabric material.
While foam supplies elasticity, it suffers from certain disadvantages. For one thing, foam tends to yellow with age if exposed. For this reason, the edges of any bra wing having a foam layer need to be sealed, for example using a sonic wheel. However, this seal tends to produce a rather sharp edge, which may cause discomfort, or at least the anticipation of discomfort on the part of the wearer.
Another disadvantage of the use of foam for forming the elastic layer of a bra strap is that foam does not exhibit an optimal modulus of elasticity, the ability of a material to snap back to its original size after being stretched, for retaining its shape over many wearer use cycles. Because of this characteristic of foam, a bra wing using foam would tend to stretch out over time.